The present invention relates to an electromagnetic contactor having plug-in connection type terminals.
FIGS. 9-11 show a conventional electromagnetic contactor: FIG. 9 is an elevation sectional view thereof; FIG. 10 is a top view; and FIG. 11 is a view showing construction of a fixed contact member. There is shown therein an arrangement of a molded housing 1, a base 2 and a pair of fixed contact members 3 disposed on each pole, the fixed contact member 3 being fitted to the housing 1 as shown in FIG. 11. More specifically, the fixed contact member 3 is fitted into a fixed-contact-member fitting portion 1a of the housing 1, the dimension Y of the U-shaped inner part of the fixed contact member 3 being smaller than the width X of the fixed-contact-member fitting portion 1a. A spring force caused by extension of the U-shaped dimension Y of the fixed contact member 3 up to the dimension X of the fitting portion 1a of the housing 1 allows the fixed contact member 3 to be fixedly fastened to the housing 1. A fixed contact 3a is fitted to one end of the fixed contact member 3 and the fixed contacts 3a are disposed opposite to respective moving contacts 4a provided on both sides of a moving contact member 4. A screw hole 3b is formed in the fixed contact member 3 and a plug-in connection type male terminal 5 is fixed to the fixed contact member by means of a clamp screw 6 screwed into the hole.
A tip 5a of the plug-in connection type male terminal 5 is formed so that a plug-in connection type female terminal (connector) (not shown) is mated with the terminal 5. A cross bar 16 is coupled to a moving iron core 7 at its lower end, and vertically and slidably holds the moving contact members 4 provided for each pole in its upper portion. A contact spring 8 is used to impart contact pressure to the moving contact member 4.
The cross bar 16 is slidably held by the housing 1 in such a manner that it is made vertically movable in FIG. 9. A fixed iron core 9 and operating coils 10 both are fixed to the housing 1 and the base 2. Kick out springs 11 are disposed so as to urge the cross bar 16 upward. Fixed screws 12 are employed to secure the housing 1 to the base 2. An operating coil 10 is wound on a coil frame 30 and a coil terminal 31 is inserted into the coil frame 30. The terminal of the operating coil 10 is connected to one end of the coil terminal 31, whereas a substantially L-shaped plug-in connection type male terminal 32 is connected to the other end of the coil terminal by means of a clamp screw 33 which is screwed into a threaded hole provided in the other end. A tip 32a of the plug-in connection type male terminal 32 is formed so that it is fitted into the plug-in connection type female terminal (not shown).
In operation, the attraction of magnetic flux generated when voltage is applied to the operating coils 10 has the moving iron core 7 attracted to the fixed iron core 9, whereby the cross bar 16 coupled to the moving iron core 7 moves against the force of the kick out springs 11 in the downward direction in FIG. 9. The moving contact member 4 held by the cross bar 16 also moves down so that their moving contacts 4a come in contact with the respective opposite fixed contacts 3a. As each part is so dimensioned as to move the cross bar slightly below the contact position, the cross bar 16 becomes slightly lower than the positions of the contacts (an over travel amount). Consequently, the contact spring 8 is compressed and the compression force is applied to the moving contact member 4 in the form of a contact pressure. As a result, the fixed contact members 3 at the left- and right-hand sides shown in FIG. 9 are electrically connected.
When the voltage applied to the operating coils 10 is switched off, the electromagnetic force between the moving iron core 7 and the fixed iron core 9 is extinguished and the cross bar 16 is caused by the force of the kick out springs 11 to move in the upward direction in FIG. 9. As a result, the contact between the moving contacts 4a and the fixed contacts 3a are broken to provide an open channel. The circuit of the electromagnetic contactor is thus opened and closed.
A description will subsequently be given to the connection and disconnection of the connectors to the plug-in connection type male terminals 5 and 32. In FIG. 9, the plug-in connection type female terminals (not shown) are inserted in direction of arrow A for connection, whereas they are pulled out in direction of arrow B for disconnection. When the plug-in connection type female terminals (not shown) are removed, however, they often remain rather firmly mated with the plug-in connection type male terminals 5 and 32. Thus, the plug-in connection type female terminals (not shown) are pulled out while they are twisted in direction of arrow C.
Since the conventional electromagnetic contactor is thus constructed, force is applied to even the fixed contact member 3 in both directions of B and C shown in FIG. 9 when the female terminal is removed from the plug-in connection type male terminal 5. This means the dimension Y of the U-shaped inner part of the fixed contact member 3 shown in FIG. 11 is increased. When the elastic stress applied to the fixed contact member exceeds limitation, the dimension Y is subjected to permanent deformation and comes up close to or exceeds the dimension X of the housing 1.
Variations of the dimension Y result in making the fixed contact member 3 loosely fixed to the housing 1 and, in the worst case, causing it to be unsteadily fixed thereto or making the over travel amount changed due to a change of position of the fixed contact 3a, or further inducing the falling off of the fixed contact member itself. For this reason, measures have to be taken to increase the force of fixing the fixed contact member 3 to the housing 1 by, for example, increasing the thickness of the plate thereof. Despite such measures are taken, there still remain some apprehensions for great force unexpectedly exerted at the time the fixed contact member 3 is removed.
When the female terminal is removed from the plug-in connection type male terminal 32, moreover, the force (in directions of arrows B, C) is applied so that the coil terminal 31 or the plug-in connection type male terminal 32 is subjected to deformation, thus making the operation impossible as the discription occurs at the terminal of the operating coil 10 connected to the end of the coil terminal 31. In addition, there are problems that a number of parts are required and it takes long time in assembly work.